Switch next solver to use a specific associated type for trait def id #145377

ChayimFriedman2 · 2025-08-14T03:22:53Z

The compiler just puts DefId in there, but rust-analyzer uses different types for each kind of item.

See the Zulip discussion. In short, it will be a tremendous help to r-a to use specific associated types, while for the solver and the compiler it's a small change. So I ported TraitId, as a proof of concept and it's also likely the most impactful.

r? types

bors · 2025-08-15T16:59:48Z

☔ The latest upstream changes (presumably #144991) made this pull request unmergeable. Please resolve the merge conflicts.

rustbot · 2025-08-16T18:50:16Z

This PR was rebased onto a different master commit! Check out the changes with our range-diff.

bors · 2025-08-20T00:23:29Z

☔ The latest upstream changes (presumably #145600) made this pull request unmergeable. Please resolve the merge conflicts.

lcnr · 2025-08-20T10:17:24Z

sorry for not replying to this PR up until now 😅

I am somewhat torn about this and avoided forming a final opinion up until now. I think this is generally useful and I am in favor of this change.

I do feel like ideally this should not limited to the solver and we actually have some struct AssocItemDefId { inner: DefId } outside of the solver as well. We already have struct BodyId for the HIR.

I feel like the main issue is to actually use these IDs everywhere 😅 I don't know what exactly I want and changing stuff here results in a lot of churn/merge conflicts

so yeah, want to take some time to properly sort out my thoughts here, am generally in favor, but don't have the time to do that rn

ChayimFriedman2 · 2025-08-21T03:51:30Z

@lcnr That's exactly why I opened this PR: so you can see (and I can be sure) that it's not, in fact, a big change.

Doing it throughout the compiler might be interesting but it definitely will be a big change, and I don't want to do that. I also didn't create this PR to have better type safety within the solver (although this is nice), but to help rust-analyzer.

lcnr

Can you rename TraitSolverLangItem to SolverLangItem?

TraitSolverTrait is hard to read.

Also, rename uses of trait_def_id to just trait_id maybe?

then r=me. While I'd like to maybe extend that to rustc, I agree that it doesn't make the trait solver harder to read and it's useful for r-a

View changes since this review

compiler/rustc_type_ir/src/predicate.rs

compiler/rustc_type_ir/src/interner.rs

rustbot · 2025-08-24T06:30:36Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

ChayimFriedman2 · 2025-08-24T06:31:25Z

@lcnr Did what you requested, except renaming all trait_def_id to trait_id because I fear this will cause a lot of conflicts, and trait_def_id is not incorrect either.

compiler/rustc_middle/src/ty/context.rs

The compiler just puts `DefId` in there, but rust-analyzer uses different types for each kind of item.

rust-log-analyzer · 2025-08-25T15:00:01Z

The job x86_64-gnu-tools failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)


warning: `test_docs` (lib doc) generated 4 warnings
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.57s
   Generated /checkout/obj/build/x86_64-unknown-linux-gnu/test/rustdoc-gui/doc/test_docs/index.html
npm ERR! code ECONNRESET
npm ERR! network aborted
npm ERR! network This is a problem related to network connectivity.
npm ERR! network In most cases you are behind a proxy or have bad network settings.
npm ERR! network 
npm ERR! network If you are behind a proxy, please make sure that the
npm ERR! network 'proxy' config is set properly.  See: 'npm help config'

npm ERR! A complete log of this run can be found in: /home/user/.npm/_logs/2025-08-25T14_59_48_442Z-debug-0.log
npm install did not exit successfully

thread 'main' panicked at src/tools/rustdoc-gui-test/src/main.rs:69:10:
unable to install browser-ui-test: Custom { kind: Other, error: "npm install returned exit code exit status: 1" }
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/788da80fcfcef3f34c90def5baa32813e39a1a41/library/core/src/panicking.rs:75:14

ChayimFriedman2 · 2025-08-25T15:35:23Z

That must be a spurious failure.

rust-log-analyzer · 2025-08-26T13:37:22Z

The job tidy failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

spellcheck files
building external tool typos from package [email protected]
finished building tool typos
npm WARN deprecated @humanwhocodes/[email protected]: Use @eslint/object-schema instead
npm ERR! code E403
npm ERR! 403 403 Forbidden - GET https://registry.npmjs.org/zod/-/zod-3.23.8.tgz
npm ERR! 403 In most cases, you or one of your dependencies are requesting
npm ERR! 403 a package version that is forbidden by your security policy, or
npm ERR! 403 on a server you do not have access to.

npm ERR! A complete log of this run can be found in: /home/user/.npm/_logs/2025-08-26T13_36_52_331Z-debug-0.log
tidy error: IO error: npm install returned exit code exit status: 1
npm install did not exit successfully
some tidy checks failed
Bootstrap failed while executing `test --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck`
Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage1-tools-bin/rust-tidy /checkout /checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo /checkout/obj/build 4 /node/bin/npm --extra-checks=py,cpp,js,spellcheck` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1583:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:1225:29

Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:02:49
  local time: Tue Aug 26 13:37:11 UTC 2025
  network time: Tue, 26 Aug 2025 13:37:11 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

lcnr · 2025-08-28T13:33:05Z

compiler/rustc_type_ir/src/fast_reject.rs

@@ -130,7 +130,7 @@ pub fn simplify_type<I: Interner>(
        ty::RawPtr(_, mutbl) => Some(SimplifiedType::Ptr(mutbl)),
        ty::Dynamic(trait_info, ..) => match trait_info.principal_def_id() {
            Some(principal_def_id) if !cx.trait_is_auto(principal_def_id) => {
-                Some(SimplifiedType::Trait(principal_def_id))
+                Some(SimplifiedType::Trait(principal_def_id.into()))


SimplifiedType::Trait should just use a TraitId? 🤔

SimplifiedType takes a DefId as a parameter, not an Interner, therefore this is harder. And it isn't really useful either - it's used only for comparisons, so a DefId poses no harm.

lcnr

final nit, then r=me

View changes since this review

lcnr · 2025-08-28T13:34:32Z

@bors delegate+

bors · 2025-08-28T13:34:36Z

✌️ @ChayimFriedman2, you can now approve this pull request!

If @lcnr told you to "r=me" after making some further change, please make that change, then do @bors r=@lcnr

ChayimFriedman2 · 2025-08-28T21:39:21Z

@bors r=@lcnr

bors · 2025-08-28T21:39:23Z

📌 Commit 38bd808 has been approved by lcnr

It is now in the queue for this repository.

bors · 2025-08-29T00:32:25Z

⌛ Testing commit 38bd808 with merge ef8d1d6...

bors · 2025-08-29T03:39:07Z

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing ef8d1d6 to master...

github-actions · 2025-08-29T03:42:21Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing f2824da (parent) -> ef8d1d6 (this PR)

Test differences

Show 6 test diffs

6 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard ef8d1d6f5bf59524a22943d9f64c002e5c883afd --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

dist-aarch64-linux: 8569.5s -> 6101.4s (-28.8%)
aarch64-apple: 6758.7s -> 5484.7s (-18.9%)
aarch64-msvc-1: 6666.7s -> 7582.3s (13.7%)
dist-apple-various: 5040.5s -> 5556.3s (10.2%)
dist-aarch64-apple: 6976.1s -> 6263.2s (-10.2%)
aarch64-gnu-debug: 5011.9s -> 4540.7s (-9.4%)
x86_64-gnu-llvm-20-1: 3539.5s -> 3208.5s (-9.3%)
dist-x86_64-msvc-alt: 8883.3s -> 9476.0s (6.7%)
i686-gnu-2: 5863.3s -> 6177.7s (5.4%)
pr-check-1: 1762.8s -> 1675.5s (-5.0%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-08-29T05:14:36Z

Finished benchmarking commit (ef8d1d6): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary -2.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.5%	[-2.5%, -2.5%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.5%	[-2.5%, -2.5%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 467.655s -> 465.841s (-0.39%)
Artifact size: 388.50 MiB -> 388.53 MiB (0.01%)

rustbot assigned lcnr Aug 14, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Aug 14, 2025

ChayimFriedman2 force-pushed the solver-def-id branch from a370dc8 to a854097 Compare August 14, 2025 03:32

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ChayimFriedman2 force-pushed the solver-def-id branch from a854097 to e854390 Compare August 14, 2025 04:42

ChayimFriedman2 force-pushed the solver-def-id branch from e854390 to 9d377f8 Compare August 16, 2025 18:50

lcnr reviewed Aug 22, 2025

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ChayimFriedman2 force-pushed the solver-def-id branch from 9d377f8 to 43692ad Compare August 24, 2025 06:30

lcnr reviewed Aug 25, 2025

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compiler/rustc_middle/src/ty/context.rs Outdated Show resolved Hide resolved

Switch next solver to use a specific associated type for trait def id

38bd808

The compiler just puts `DefId` in there, but rust-analyzer uses different types for each kind of item.

ChayimFriedman2 force-pushed the solver-def-id branch from 43692ad to 38bd808 Compare August 25, 2025 13:52

lcnr closed this Aug 26, 2025

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 26, 2025

lcnr reopened this Aug 26, 2025

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 26, 2025

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rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 26, 2025

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rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 26, 2025

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lcnr added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 28, 2025

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 28, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Aug 29, 2025

bors merged commit ef8d1d6 into rust-lang:master Aug 29, 2025
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rustbot added this to the 1.91.0 milestone Aug 29, 2025

ChayimFriedman2 deleted the solver-def-id branch August 29, 2025 03:49

Switch next solver to use a specific associated type for trait def id #145377

Switch next solver to use a specific associated type for trait def id #145377

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Overall result: no relevant changes - no action needed

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